Boxwood cultivar named ‘Arctic Emerald’

ABSTRACT

A new and distinct  Buxus  cultivar is provided. The attractive evergreen hedge/shrub displays a dense columnar, somewhat pyramidal, upright growth habit, and is particularly fast growing relative to many other  Buxus  variants. No pruning is required to maintain the attractive growth habit. The new variant commonly displays a single sturdy trunk or a multi-trunk base, depending on the cutting at time of propagation, that develops multiple pliable fast-growing branches with glossy deep green foliage. The foliage displays deep green color in all weather conditions, temperatures, and degrees of sunlight and shade. The new variant exhibits excellent endurance to both high and low temperatures, and has exceptional tolerance to wind, snow, and ice due in part to the yielding characteristic of its branches. No typical boxwood fragrance is emitted by the foliage or branches. The new variant&#39;s growth habit and shape make it suitable for a multitude of landscape and other uses.

Genus/species: Buxus sempervirens.

Varietal denomination: ‘Arctic Emerald’.

SUMMARY OF THE INVENTION

The present disclosure relates to a new and distinct Buxus cultivar thatwas discovered in nature around 1993 in Brackenridge, Pa., and wasselected and asexually propagated. The parentage of the new cultivar isuncertain. However, it may be the result of a naturally occurring wholeplant mutation of an existing but unidentified Buxus variety(unpatented).

A single plant of the new cultivar was asexually propagated, selected,and preserved having the distinctive characteristics discussedhereinafter. Had the new cultivar of the present invention not beenpropagated and preserved, it would not have been available to mankind.

Upon careful observation and testing, the new cultivar of the presentinvention was found to express the following combination ofcharacteristics:

-   -   (a) assumes a dense, columnar, somewhat pyramidal, upright        growth habit;    -   (b) lacks typical boxwood foliage fragrance;    -   (c) exhibits an unusually rapid growth cycle following asexual        propagation from a cutting;    -   (d) exhibits an exceptionally strong and hardy root system;    -   (e) exhibits glossy deep olive green foliage throughout the year        in high and low temperatures, and does well in full sun, partial        sun, and shade, without any substantial change in coloration        during the winter;    -   (f) exhibits excellent all-season hardiness to at least U.S.D.A.        Plant Hardiness Zone 5, and likely to Zone 4; and    -   (g) exhibits exceptional tolerance to wind, ice and snow due, at        least in part, to the yielding character of its pliable        branches.

The new cultivar is a dense upright columnar, somewhat pyramidal,broadleaf evergreen that is capable of being grown and maintained as anattractive ornamental outdoor plant throughout the year. A ratio ofheight to width of approximately 7:3 is common in older plants. To date,the typical size of fully mature plants is unknown. The new cultivartypically displays a single sturdy base or a multi-trunk base, dependingon the cutting at the time of propagation, that develops abundantslender fast-growing compact pliable multi-budded branches. It is fastgrowing, and two-year old plants, growing in optimal soil conditions,have exhibited up to about 24 inches of new upright branches. Nurserystock may be started in containers, and at from 2 to 5 years old will beof sufficient size for the sales market. 8-month old establishedcuttings can be planted in the ground, typically without protection, andready for the sales market in about 1 year, although such plantsnecessarily will be rather small.

The foliage is found to be lacking in typical boxwood fragrance, andsuch an absence of fragrance is preferred by some growers. Also, as withother boxwood cultivars, birds, rabbits, and deer tend to dislike andare repelled by the foliage and branches of the new cultivar.

The glossy, deep green foliage is maintained throughout the year, eventhrough the winter. The new cultivar resists a common tendency ofcertain known boxwood cultivars to assume a brownish-green colorationduring the winter, and the new cultivar has been shown to display aglossy deep green coloration even in single digit (Fahrenheit)temperatures. The new cultivar exhibits a light bronze olive green intimes of winter thaws, and exhibits deep green coloration in extreme hotand cold weather (see, for example, FIG. 5).

The new cultivar has demonstrated exceptional all-weather hardiness, aswell as extraordinary tolerance to wind, ice, and snow, which is atleast in part due to its strong and hardy root system and pliable,yielding character of its branches. It has been shown to haveexceptional winter tolerance to at least U.S.D.A. Plant Hardiness Zone5, and probably is hardy to Zone 4. Good resistance to winter burn alsois exhibited. The new cultivar does not require protection throughoutthe range of typical weather conditions during the year. The foliage ofthe new cultivar exhibits tones of olive green during winter temperaturechanges. The hardiness of the new cultivar equals or exceeds that ofpreviously known boxwood cultivars known for superior hardiness. Itsstrong columnar growth habit keeps its general shape, without pruning,in all seasons. Even though severe weather conditions may cause theplants to bend over, the plants spring back into shape after, forexample, snow and/or ice on the plants melts (for example, compare FIG.2 versus FIG. 1). In comparison, Buxus sempervirens ‘Graham Blandy’(unpatented in the United States), likely hardy to U.S.D.A. HardinessZone 5, which has a straight-sided narrow growth habit, may requirepruning to maintain its slender shape after Spring growth, when rainssometimes pull down the new growth.

The new cultivar is exceptionally sturdy, withstanding coldtemperatures, snow, and ice. The plants typically rebound without damageto the multiple pliable branches of its columnar, somewhat pyramidalgrowth habit. The new cultivar's Spring growth yields without damage toits form during rains, and requires no pruning during rains. This may becontrasted with the ‘Graham Blandy’ boxwood, which has branches thattend to fall during heavy rains, and which may require pruning afterrains to retain its characteristic slender sides.

The new cultivar can be grown to advantage as attractive ornamentationin various landscapes, and is particularly well suited for use in theformation of a privacy hedge, or privacy wall, due to its dense foliage,rapid upright growth habit, columnar, somewhat pyramidal shape, andheight. Its exceptional growth habit, density, and columnar, somewhatpyramidal shape do not require pruning, although it may be pruned tosuit particular landscape needs. The new cultivar would do well assingle plants and as multiple-plant groupings in landscaping aroundcommercial and residential structures due to its rapid growth habit andcolumnar, somewhat pyramidal shape relative to other boxwood variantshaving less upright shapes. The new cultivar's rapid growth habit andcolumnar, somewhat pyramidal shape makes it suitable for various usesbecause it adapts well in sun, partial sun, and shade. Its branches arestrong and flexible, withstanding heavy rain, ice, and snow, making atadaptable to and exhibiting good growth in north, south, east and westexposures, and avoiding the necessity for covering the plants duringsevere weather. This contrasts with, for example, Buxus sempervirens‘Green Velvet’ (unpatented in the United States), which is relativelyless dense and which, when planted with a southern exposure, is prone toslower growth, achieving less height and width. Also, in comparison tothe new cultivar, the ‘Graham Blandy’ boxwood does not grow well in fullsun. The new cultivar is suitable for various types of border plantings,including low and high landscape borders, and as an enhancement to otherplants, including, for example, flowering plants and evergreens of othergreen to blue hues. Much of the plant displays foliage that hasrounded-tip leaves, but as the plant ages spear-like leaves also may bedisplayed. The compactness and density of the new variant's smallbroad-leaf rounded tip and spear-like tip foliage make it a suitablechoice for topiaries. The new variant's glossy deep green broad-leafrounded tip and spear-like tip foliage distinguish it from many knownboxwood varieties, including Buxus sempervirens ‘Richard’ (unpatented),which has deep green heart-shaped leaves.

The new cultivar has been tested at Brackenridge, Pa. and NatronaHeights, Pa. since 1993, and at West Grove, Pa. since 2001. The newcultivar also has been tested, and its hardiness and other propertiesobserved, in all season weather conditions in the states of California,Maryland, Michigan, North Carolina, Ohio, Oklahoma, Oregon, andWashington, as well as in the District of Columbia, France and TheNetherlands since 2001-2002 and up to the present. It has been observedthat ‘Arctic Emerald’ plants include both spear-shaped leaves androunded oval-like leaves, including some oval-like leaves including anindentation in the top center of the leaves. In contrast, Englishboxwood includes rounded leaf tips sometimes, but not always, having asplit in the top center of the leaf. ‘Arctic Emerald’ has exhibited afast, tall growth habit, while English boxwood generally exhibits aslower, shorter growth habit.

When compared with the ‘Graham Blandy’ boxwood, which is astraight-sided narrow tall upright plant with a narrow base and islikely hardy to U.S.D.A. Plant Hardiness Zone 5, the new cultivarexhibits a tall columnar habit with a relatively wide base, is likelyhardy to Zone 4, and has achieved a height of 7½ feet and width of 36inches feet at 11 years and 4 months (see, for example, FIG. 1). The newcultivar exhibits extraordinary growth without pruning, and pruning isnot required to maintain the shape of the plants in harsh weatherconditions. The new cultivar has been raised outdoors from 2½ inch plantcuttings in Zone 5 without protection and with, at times, temperaturescomparable to Zone 4. Certain specimens of the new cultivar haveexhibited accelerated growth after 8 years.

Buxus sempervirens ‘Arctic Emerald’ displays deep green, dense foliagewith a fast growing habit withstanding high and low temperatures inU.S.D.A. Plant Hardiness Zone 5, with possible hardiness to Zone 4. Thenew variety does well in full sun, partial sun, and shade. It issuitable where privacy is desired and as a hedge, specimen, or containerplant, having a mature height of about 10 feet and a mature width ofabout 4 feet. In comparison, Buxus sempervirens ‘Prostrata’ (unpatented)grows to a relatively short height, spreading like a ground cover, andis known to have a mature height of about 3 feet and a spread of about10 feet. Buxus sempervirens ‘Graham Blandy’ displays a slender and tallgrowth habit, having a mature height of about 15 feet to 18 feet. Buxussempervirens ‘Elegantissima’ (unpatented) is variegated, with maturesize of about 7 feet tall and 7 feet wide.

The unusually fast growth habit of the new cultivar after asexualpropagation from a cutting is particularly noteworthy. For instance,attractive dense columnar plants produced from cuttings in 1-galloncontainers commonly assume a height of 18 inches or more, and a width of4 to 5 inches within 2 years following asexual propagation. The newcultivar's particularly rapid growth habit following propagation rendersit well suited for commercial production in containers. Expected size of5 to 6 year old plantings is about 52 inches high by 18 inches wide.

Asexual reproduction of the new cultivar by the use of cuttings has beencarried out at Brackenridge, Pa. and at West Grove, Pa. Such propagationhas confirmed that the unique combination of characteristics of the newcultivar has been stably established and is well transmitted tosuccessive generations. The new variety reproduces true to type insuccessive generations of asexual reproduction.

The new cultivar has been named ‘Arctic Emerald’.

BRIEF DESCRIPTION OF THE PHOTOGRAPHS

The accompanying photographs show as nearly true as is reasonablypossible to make the same, in color illustrations of this character,typical specimens of the new cultivar.

FIG. 1 is a photograph of several mature “mother” plants of the ‘ArcticEmerald’ cultivar during April 2004 while being grown outdoors withoutcover for test purposes in a residential lot concealed from public viewin Brackenridge, Pa. The plants had been started as 2½ inch cuttings inthe lot in the Summer of 1993, and in the photograph are approximately7½ feet tall and approximately 36 inches wide. The new cultivar'scolumnar shape, compact branches and foliage, and dense glossy deepgreen foliage are illustrated.

FIG. 2 is a photograph of the same plants as shown in FIG. 1, in thesame location, but taken in December 2003. The plants are covered byheavy snow and are nearly bent in half. The bluish tinge to the newcultivar's foliage that is developed in cold weather is illustrated.Comparison of FIGS. 1 and 2 illustrates the ‘Arctic Emerald’ cultivar'sextraordinary cold weather hardiness and tolerance to snow and ice.

FIG. 3 is a photograph of several 41-month old plants of the ‘ArcticEmerald’ cultivar during April 2004 while being grown outdoors withoutcover for test purposes in a residential lot concealed from public viewin Brackenridge, Pa. The plants were begun in October 2000 from cuttingsin the position illustrated. The new cultivar's columnar, somewhatpyramidal growth habit, dense glossy deep green foliage, and compactbranches are illustrated.

FIG. 4 is a photograph of the same plants as shown in FIG. 3, but wastaken in December 2003. The 38-month old plants are shown covered inheavy snow. Comparison of FIGS. 3 and 4 illustrates the ‘Arctic Emerald’cultivar's extraordinary cold weather hardiness and tolerance to snowand ice.

FIG. 5 is a photograph of several 52-month old plants of the ‘ArcticEmerald’ cultivar during a night in February 2005 while being grown fortest purposes in a residential lot concealed from public view inBrackenridge, Pa. The plants had been planted in place in October 2000.The plants are approximately 3½ feet tall and 14 inches wide at theirwidest point. Despite the single-digit Fahrenheit temperature at thetime of the photograph, the plants exhibit their characteristic glossydeep green foliage. The upright dense growth habit in the absence ofpruning also is illustrated.

FIG. 6 is a photograph of several 14-month old plants of the new ‘ArcticEmerald’ cultivar during November 2001 while being grown for testpurposes in a test bed concealed from public view in Natrona Heights,Pa. The cultivar's tall columnar growth habit, glossy deep greenfoliage, and rounded leaf tips are illustrated.

FIG. 7 is a photograph of several plants of the new ‘Arctic Emerald’cultivar during March 2003 while being grown in a test bed in aresidential lot concealed from public view in Brackenridge, Pa. Theplants were started as 2½ inch cuttings planted in the bed 8 monthsbefore the photograph was taken. The photograph shows the plants after3-inch thick ice had covered the test bed and the cultivar's hardynear-surface root system for a period of over two weeks. The plantsexhibit a bluish tinge to the glossy deep green foliage. The cultivar'stolerance to and hardiness in cold temperatures and ice are illustrated.

FIG. 8 is a photograph of the same plants as shown in FIG. 7 in the sametest bed, but during April 2004. The plants are shown in 21 months oldand were grown outdoors without protective cover. The plants evidence nodamage from the winter temperatures and ice shown in FIG. 7. Also, thecultivar's columnar growth habit, and glossy deep green and densefoliage are illustrated.

FIG. 9 is a photograph of the ‘Arctic Emerald’ cultivar during April2004 which being grown for test purposes in a residential lot concealedfrom public view in Brackenridge, Pa. The plant is shown approximately17 months old. The new cultivar's dense foliage, columnar growth habit,and glossy deep green coloration, here with a bluish tinge, areillustrated. The plants is shown with multiple buds of new growth, whichcontribute to the dense and compact growth habit of the new cultivar.

FIG. 10 is a photograph of a cutting from a 54-month old plant of the‘Arctic Emerald’ cultivar taken during February 2005 while the plant wasbeing grown for test purposes in a residential lot concealed from publicview in Brackenridge, Pa. The temperature was 35° F. at the time thecutting was taken. The new cultivar's deep green foliage with roundedleaf tips, cold weather hardiness, and excellent growth uniformity areillustrated. Three of the four bottommost leaves on the leftmost branchalso show the lighter green color of the underside of the foliage.

FIG. 11 is a photograph of an approximately 4 year old plant of the‘Arctic Emerald’ cultivar taken on Sep. 21, 2005. The plant is shown ina 3 gallon container.

DETAILED DESCRIPTION

The following is a detailed description of the new cultivar of thepresent invention which was prepared while observing 11½ year old plantsgrowing in a residential lot in Brackenridge, Pa., concealed from publicview. Color terminology is in accordance with the R.H.S. Colour Chart ofThe Royal Horticultural Society, London, England, except where generalterms of ordinary dictionary significance are used.

-   Type: Extraordinarily hardy broad-leaf evergreen shrub with strong    hardy near-surface root system, suitable for garden decoration,    formal and general landscape use, and container plantings.-   Botanical classification: Buxus sempervirens cultivar of uncertain    parentage, which was discovered in nature around 1993 in    Brackenridge, Pa., and was selected and asexually propagated. It is    believed that the cultivar may be the result of a naturally    occurring whole plant mutation of an existing but unidentified Buxus    variety (unpatented). The new cultivar has been named ‘Arctic    Emerald’.-   Growth habit: Fast growing, columnar, somewhat pyramidal, dense    foliage, and upright, with compact pliable branches. The plant    height commonly exceeds plant width, with a common mature plant    height-to-width ratio being approximately 7:3. A more rapid growth    cycle than most other Buxus cultivars commonly is observed, with    added growth throughout the Spring and into the Fall growing    seasons.-   Plant dimensions: 11½ year old plant commonly assumes a height of    approximately 7½ feet and a width of approximately 3 feet. Older    plants will assume taller height, and a maximum height has not yet    been observed. More rapid growth has been observed for plants of 8    years or more.-   Propagation: The new cultivar holds its distinguishing    characteristics through succeeding propagations by asexual    propagation methods, such as the rooting of vegetative cuttings.-   Juvenile foliage:    -   -   Size.—Approximately 0.75 inch in length on average.        -   Shape.—Generally oval-shaped, with a cuneate base and a            rounded apex.        -   Margin.—Entire.        -   Winter color.—Upper surface: Yellow-Green Group 147A. Lower            surface: Yellow-Green Group 144A with a mid-rib of Green            Group 137C.        -   Spring color.—Upper surface: Yellow-Green Group 147A. Lower            surface: Yellow-Green Group 144A, with a mid-rib of Green            Group 137C.        -   Summer color.—Upper surface: Green Group 137A. Lower            surface: Green Group 138B, with a mid-rib of Yellow-Green            Group 144A.        -   Fragrance.—None.        -   Quantity.—About 30 or more leaves per 4 inches of branch            length.        -   Venation.—Approximately ⅞ inch smooth and glossy veins            arranged in an outwardly-directed diagonal slant pattern on            both upper surface and underside of leaf. Upper surface:            Yellow-Green Group 147 A. Underside: Yellow-Green Group            146A.-   Mature foliage:    -   -   Size.—Approximately 1.25 inches in length on average and            approximately 0.5 inch in width on average.        -   Shape.—Generally oval-shaped, with a cuneate base and a            generally rounded apex.        -   Margin.—Entire.        -   Winter color.—Upper surface: Yellow-Green Group 147A. Lower            surface: Yellow-Green Group 144A, with a mid-rib of Green            Group 137C.        -   Spring color.—Upper surface: Yellow-Green Group 147A. Lower            surface: Yellow-Green Group 144A, with a mid-rib of Green            Group 137C.        -   Summer color.—Upper surface: Green Group 137B. Lower            surface: Yellow-Green Group 144A, with a mid-rib of            Yellow-Green Group 144A.        -   Fragrance.—None.        -   Quantity.—Approximately 60 leaves per each 5 inches of            branch, with extending new patterns of growth providing            dense gatherings of new branches and leaves.        -   Venation.—Approximately ⅞ inch smooth and glossy veins            arranged in an outwardly-directed diagonal slant pattern on            both upper surface and underside of leaf. Upper surface:            Yellow-Green Group 147 A. Underside: Yellow-Green Group            146A.-   Juvenile stem: May have 1-5 vertical stems. Stems vary from about    4-6.5 inches up to about 22-26 inches in length. Typical internode    length is about 3-5 inches. Smooth texture. Color: Green Group 139 A    on upper stem and Green Group 139B on lower stem.-   Mature stem: Typical length is about 36 inches. Typical internode    length is 12 inches. Smooth texture. Color: Green Group 139 A on    upper stem and Green Group 139B on lower stem.-   Juvenile branches:    -   -   Color.—Yellow-Green Group 147A.        -   Diameter.—Approximately 0.4 cm on average.        -   Number.—Typically 10-12 branches per plant.        -   Internode length.—Typically 3-5 inches.        -   Texture.—Smooth.-   Mature branches:    -   -   Color.—Green Group 138B.        -   Diameter.—Approximately 1.5 cm on average.-   Juvenile petioles: Average length 6 to 8 inches. Average diameter    approximately 1/16 inch. Smooth texture. Color: Yellow-Green Group    147B.-   Mature petioles: Average length 5 to 9 inches. Average diameter just    under 0.125 inch. Smooth texture. Color: Green Group 133B.-   Inflorescence: Observed plants of age 8 years old and up to last    observation at 11½ years exhibit small non-fragrant clusters of    cream-colored blossoms (Yellow-White Group 158D in cold conditions).    Each blossom develops into a seed pod of two half-moon shaped seeds    per pod. Pods are cream-colored (Grey-Brown Group N 199C) with a    straw-like texture, and seeds within a pod are extremely hard and    exhibit a cream-colored outer surface (concave side color:    Grey-Orange Group 164B; and convex side color: Grey-Orange Group    164C).-   Flower buds: Mature flower buds hardy to U.S.D.A. Plant Hardiness    Zone 5, and possibly to Zone 4. Average bud diameter is about 0.375    inch. Average bud length is about 0.375 inch. Overall form/shape of    buds is an open “burst” pattern. Bud surface is sateen. Color:    Yellow-White Group 158D.-   Reproductive organs:    -   -   Pistils.—A single pistil per female flower. Each pistil            includes 1 ovary (including 3 fused locules) and 3 free            styles (each having a bilobed stigma). Typical ovary length            is approximately 2220 micrometers, and typical ovary            diameter is approximately 2330 micrometers. Typical style            length is approximately 1130 micrometers, and typical style            width (at base) is approximately 1200 micrometers. Typical            stigma length is approximately 1390 micrometers, and typical            stigma width is approximately 1360 micrometers.        -   Stamens.—4 stamens per male flower, each stamen including a            filament and an anther. Filament color is RHS Colour Chart            Yellow Group 11D, and anther color is RHS Colour Chart            Yellow Group 5A. Typical filament length is approximately            2040 micrometers, and typical filament width is            approximately 470 micrometers. Typical anther length is            approximately 1770 micrometers, and typical anther width is            approximately 1270 micrometers.        -   Pollen.—Pollen is abundant, typically with hundreds of            pollen grains per stamen. Pollen is RHS Colour Chart Yellow            Group 5A.-   Development:    -   -   Hardiness.—Has been tested hardy to U.S.D.A. Plant Hardiness            Zone 5, and it is believed it may hardy to Zone 4. As            observed at Brackenridge, Pa., the new cultivar has well            withstood winter temperatures at least as low as −2° F.,            wind chill factors of −25° F., wind forces of 55-60 miles            per hour, and summer temperatures at least as high 96° F.,            all without any sign of damage to the foliage or other parts            of the plants.        -   Disease resistance.—No disease problems have been observed            by the inventor to date.        -   Insect tolerance.—No insect damage has been observed by the            inventor to date.

1. A new and distinct variety of Boxwood plant possessing the followingcharacteristics: (a) assumes a dense, columnar, somewhat pyramidal,upright growth habit; (b) lacks typical boxwood foliage fragrance; (c)exhibits an unusually rapid growth cycle following asexual propagationfrom a cutting; (d) exhibits an exceptionally strong root system; (e)exhibits glossy deep olive green foliage substantially throughout theyear in high and low temperatures, and does well in full sun, partialsun, and shade, without any substantial change in coloration during thewinter; (f) exhibits excellent all-season hardiness to at least U.S.D.A.Plant Hardiness Zone 5; (g) exhibits exceptional tolerance to wind, iceand snow due, at least in part, to the yielding character of its pliablebranches; substantially as herein shown and described.